1. Technical Field
This invention relates generally to a system carried on a vehicle for collecting, condensing, storing, and distributing volatile fuel vapors, and more particularly such a system that condenses volatile fuel vapors by compression and cooling to form a liquid fuel stored in a condensate tank for use as a desirable fuel for cold start engine operation.
2. Background Art
Currently, vehicle fuel systems are unable to contain volatile fuel vapors that escape during their refueling process. The vapor space in the tank is displaced by the entering liquid fuel, and fuel vapors are purged out of the fuel pipe to the atmosphere. In addition to vapors lost during refueling, changing ambient conditions allow liquid fuel to vaporize within the tank. These vapors are generally stored in charcoal canisters on the vehicle and are later drawn into the engine intake and consumed during cruise conditions. During hot weather and/or during long engine idle periods, such as in heavy traffic, the charcoal canisters can become saturated and vent fuel vapors to the atmosphere, resulting in excessive evaporate emissions. To contain all of the vapors generated by the worst case scenario, a charcoal canister would have to be prohibitively large.
One attempt to limit the escape of volatile emissions to the atmosphere during refueling is described in U.S. Pat. No. 3,752,355 issued Aug. 14, 1973, to Joseph Weissenbach, titled Contained Volatile Liquids Vapor Retention System. The Weissenbach system proposes the use of a flexible bag in a fuel tank to provide a variable air chamber separate from the fuel disposed in the tank. The flexible container is sealed to the body of a breather tube which allows air to enter or be discharged from the bag, and accordingly the volume of the air chamber bag to change as the fluid level rises and falls in the tank.
Other devices proposed to control vapor emission during transfer of fuel from a stationary storage tank to a vehicle are described in U.S. Pat. No. 3,581,782, issued Jun. 1, 1971, to George R. Onufer, titled Vapor Emission Control System; U.S. Pat. No. 3,919,857, issued Nov. 18, 1975, to Richard A. Nichols, et al, entitled Apparatus for Melting Ice in a Gasoline Vapor Recovery System, describing a method and apparatus for melting ice in the bottom of an absorber in a vapor recovery system when transferring fuel between tanks, and U.S. Pat. No. 3,921,412, issued Nov. 25, 1975, to Stephen D. Heath, et al and entitled Vapor Recovery Apparatus Employing Dispensing Nozzle with Condensing Capacity.
None of the above-described systems are appropriate for on-board vapor recovery systems which are expected to be needed to meet ever-increasingly stringent vehicle evaporate emissions standards. It is desirable to have an effective way to control fuel vapors in a closed fuel system which not only limits the vapor space above the liquid fuel, but also condenses any vapors into a liquid fuel which can be stored for later specific use, such as a highly desirable fuel for cold start engine operation. It is also desirable to have a fuel vapor control system in which the volatile fuel vapors are pressurized as they are drawn from the fuel tank and then condensed to a liquid state for storage in an auxiliary condensate tank. It is also desirable to have a fuel delivery system which selectively delivers a supply of the primary fuel to the vehicle engine during normal operation, or provides condensed fuel vapors for cold engine starting conditions.
In accordance with one aspect of the present invention, an on-board fuel vapor collection, condensation, consideration, storage and distribution system for a vehicle includes a fuel tank containing a source of liquid fuel for normal operation of an engine of the vehicle, and a fuel vapor condensate tank. A vent valve is disposed in fluid communication with the fuel tank and is adapted to release only fuel vapor from the fuel tank. A fuel vapor compressor is disposed in fluid communication with the vent valve and a heat exchanger is disposed in fluid communication with the fuel compressor and the fuel vapor condensate tank. The heat exchanger is adapted to receive condensed fuel vapor from the compressor, condense the compressed field vapor to form a liquid fuel condensate, and deliver the resulting condensate to the condensate tank. The system further includes a fuel supply solenoid valve and a fuel return solenoid valve, both in fluid communication with the engine of the vehicle. A primary fuel supply conduit provides fluid communication between the fuel tank and the fuel supply solenoid and has a first fuel pump operatively disposed in-line with the primary fuel supply conduit. A condensate supply conduit provides fluid communication between the fuel vapor condensate tank and the fuel supply solenoid. A primary fuel return conduit is disposed in fluid communication between the fuel return solenoid valve and the fuel tank, and a condensate return conduit is disposed in fluid communication between the fuel return solenoid valve and the fuel vapor condensate tank. A second fuel pump is operatively interposed in the condensate return conduit.
Other features of the fuel vapor collection, condensation, storage, and distribution system embodying the present invention includes the fuel tank of the system having an internally disposed flexible bladder. The flexible bladder is arranged to receive a supply of liquid fuel from an external source and defines a volumetrically variable chamber within the fuel tank for storing the liquid fuel. The vent valve, in fluid communication with the fuel tank, is in direct fluid communication with the volumetrically variable chamber defined within the bladder. Other features of the fuel vapor collection, condensation, storage and distribution system embodying the present invention include the fuel vapor condensate tank having a sensor arranged for measuring the liquid level of the condensate in the fuel vapor condensate tank, and a sensor for measuring the pressure present in the fuel vapor condensate tank.
In another aspect of the present invention, an on-board fuel vapor collection, condensation, storage and distribution system for a vehicle includes a means for compressing and condensing fuel vapors formed in the fuel tank, a fuel vapor condensate tank adapted to receive condensed fuel vapors from the means for compressing and condensing fuel vapor formed in the tank, a first valve means for controllably directing a flow of fuel from at least one of the fuel tank and condensate tank to the engine, and a second valve means for controllably directing a flow of unused fuel from the engine to one of the fuel tank and condensate tank.
Other features of the on-board vapor system include the means for compressing and condensing fuel vapors formed in the fuel tank having a vent valve in fluid communication with the fuel tank, a fuel vapor compressor in fluid communication with the vent valve, and a heat exchanger in fluid communication with the fuel vapor compressor and the fuel vapor condensate tank. The heat exchanger is adapted to receive condensed fuel vapor from the compressor, condense the compressed fuel to form a liquid condensate, and deliver the resultant condensate to the condensate tank.
Still other features of the on-board fuel vapor system embodying the present invention include the first valve means for controllably directing a flow of fuel from at least one of the fuel tank and the condensate tank to the engine being a fuel supply solenoid valve, a primary fuel supply conduit providing fluid communication between the fuel tank and the fuel supply solenoid valve, and a condensate supply conduit providing fluid communication between the condensate tank and the fuel supply solenoid valve. A first fuel pump is operatively interposed in the primary fuel supply conduit.
Still other features of the on-board fuel vapor system embodying the present invention include the second valve means for controllably directing a flow of unused, or bypassed, fuel from the engine to either the fuel tank or the condensate tank being a fuel return solenoid valve, a primary fuel return conduit providing fluid communication between the fuel return solenoid valve and the fuel tank, and a condensate return conduit providing fluid communication between the fuel return solenoid valve and the fuel vapor condensate tank. A second fuel pump is operatively disposed in condensate return conduit.
Still other features of the on-board fuel vapor collection system embodying the present invention include the fuel condensate tank having a sensor for measuring the liquid level of condensate in the fuel condensate tank and a pressure sensor for measuring pressure in the fuel vapor condensate tank.